The present invention generally relates to a vehicle control apparatus, and more particularly, relates to a vehicle control apparatus in which when the control apparatus is tested, it can be confirmed whether or not the output signals are produced correctly in accordance with the input signals, and the control specifications for the particular control apparatus can be checked in a short time.
Recently, a variety of vehicle control apparatuses using microcomputers have come to be used. For example, as an example of such a vehicle control apparatus, an engine air-fuel ratio control apparatus comprising blocks of a CPU (central processing unit), a RAM (random access memory), a ROM, an A/D (analogue-to-digital) converter, an I/O (input/output) unit, etc. is disclosed in "Automobile Technology" Vol. 38, No. 2, 1984, page 158.
A variety of control specifications are required for such engine control apparatuses in accordance with the kind of vehicle, the kind of engine capacity, the kind of transmission, and so on, and there has been a demand for various kinds of engine control apparatuses which can satisfy various requirements.
The demand can be satisfied by changing the procedures or control specifications stored in a ROM provided in the engine control apparatus without changing the circuit arrangement of the engine control apparatus. Accordingly, standardization of the engine control apparatus can be effected and low cost can be expected by mass production.
When the thus arranged control apparatus is tested individually or as a unit, it is necessary to test the control apparatus to determine whether or not the control apparatus can function correctly from the outside thereof through terminals of the control apparatus.
For example, in some cases, the test can be made only through a connector to which an outside connector can be connected from the outside of the apparatus, after a control circuit printed on a substrate has been received in a housing and the parts number for identification has been indicated on the housing.
In such cases, in order to determine the control specifications stored in a ROM in the control apparatus, it is necessary to make a judgment on the basis of an externally inspected difference in operation as a difference in control specification. In order to identify the king of control apparatus (i.e., the kind or type of control specifications stored therein) among a variety of control apparatuses in which the respective control specifications are varied from one another in control data, however, there have often been difficulties in execution of the test correctly. For example, the method of test has been complicated, and a prohibitive amount of time has been taken for the test, etc.
In those cases, however, there is a case where ROMs, storing the control specifications, which have been subject to unit test in advance are used in the control apparatuses and the operation of various input/output terminals of the control apparatuses can be tested in a short time regardless of the partial variations in control specifications, and therefore a difficulty results in only distinguishing the partial variations in control specifications.
For example, in a case where the stored control specifications are only in the point that the two kinds of control apparatuses have time data of 10 minutes and 20 minutes respectively, there has been a problem in that it is impossible to distinguish the two control apparatuses unless one of the control apparatuses is caused to operate for at least 10 minutes. Thus, it takes a very long time to execute the test. This difficulty has been a serious problem in mass-production of control apparatuses.